This case series reinforces the general consensus that phosphodiesterase type 5 (PDE5) inhibitors are contraindicated in patients with a history of unilateral nonarteritic anterior ischemic optic neuropathy (NAION).

This is believed to be the largest case series published to date of NAION in patients who used the PDE5 inhibitor sildenafil (Viagra) for a prolonged period.

Subjects included 10 NAION patients 38 to 70 years old in Saudi Arabia who used sildenafil at least two to three times per week during the weeks or months prior to the onset of vision loss.

Despite the initial first episode of NAION in one eye, they all continued to use the medication and developed a second episode of NAION in the contralateral eye. Only one of these 10 patients presented with bilateral simultaneous NAION.

Nine of the patients were diabetic and some of them had other cardiovascular risk factors. The authors conclude that these patients had a greater risk of developing NAION following the use of sildenafil compared with normal healthy individuals.

They also conclude that these cases confirm the current consensus that patients who develop NAION in one eye in conjunction with PDE5 inhibitor use should be advised to discontinue the use of this medication because of the risk of fellow eye involvement.

As previously reported, they note that some patients don't report PDE5 inhibitor use due to embarrassment, especially if the patient’s wife or child is present during the consultation. They recommend ophthalmologists assessing a patient after an episode of unilateral ischemic optic neuropathy inquire about the use of these drugs.